Method of making metal balls



Oct. 21, 1952 E. DEiJssEN 2,614,317

METHOD OF MAKING METAL BALLS Filed Jan. 7, 1950 06a Mazda 44w )zfim Z pl j 1- 3 FIG. I PIC-3.5 6

INVENTOR EMIL DEUSSEN ATTORNEYS Patented Get. 21, 1952 Application January '1, 1950, Serial No. 137,418 In Germany August 19, 1949 2 Claims. 1

This invention relates to the manufacture of metal balls, particularly balls for use in bearings.

In the manufacture of metal balls for bearings the customary procedure at the present time is to form the balls from slugs cut from the end of a wire of a diameter somewhat less than the diameter of the finished ball. These slugs are shaped in semispherical dies and the total mass or volume of the slug is greater than the cubic content of the semispherical dies when brought together to form a hollow sphere, the surplus metal protruding between the dies when the dies are brought together in the form of a ring or 001- lar surrounding the equator of the ball. This surplus ring of metal is then ground off to form a sphere somewhat larger than the diameter of the finished ball. These over-sized ba11s are then tempered to the desired hardness and are then ground and polished to produce balls of the desired size, accurate spherical contour and high degree of smoothness required for bearing balls.

The above described process which is now in general use involves a considerable loss of metal and also requires two grinding operations, namely, the first grinding to remove the band or collar around the middle of the ball and the final grinding to reduce the ball to accurate size and finish. This process also has the disadvantage of producing a grain structure in the metal of the ball which significantly limits the life of the ball. The grain surface of the ball at the equator where the collar or band is formed is very difierent from the grain structure at what may be termed the poles of the ball and is also quite difierent from the grain structure of the intermediate portions between the poles and the equator with the result that under the pressure and wear of service faults develop in the surface where the difierences in grain structure occur before the wear so reduces the diameter of the ball as to require replacement.

By the im roved method forming the subjectmatter of this application the loss of metal is reduced, the procedure is simplified by the elimination of one grinding operation, and the grain structure of the ball is so improved that the balls seldom break down in the manner above described before the ball as a whole is so worn as to require replacement.

In the accompanying drawings I have illus trated in Fig. 1 the die-shaping operation as customarily employed in the manufacture of ball bearings according to present-day methods; Fig. 2 is a view similar to Fig. 1 showing primarily the displacement of the metal between the dies at an intermediate stage in the shaping operation; Fig. 3 is similar to Fig. 1 showing the dies closed;

Fig. 4 is a. sectional view on an enlarged scale showing a typical grain structure in balls manu-. iactured in accordance with the procedure illustrated in Figs. 1 to 3; Fig. 5 is a view similar to Fig. 1, but showing the first step in my improved method of manufacture; Fig. 6 is a view similar to Fig. 2, showing the shaping dies in an intermediate stage of the operation; Fig. 7 is a similar View showing the dies closed; and Fig. 8 is a sectional view on an enlarged scale showing the grain structure ofthe balls made by my improved method. 1

Referring to the drawings, I and 2 represent the two halves of co-operating dies whose shaping faces are of semispherical contour as shown by dotted lines 3. The dies are designed to be used in any conventional form of press and in the commerical manufacture of bearing balls the dies are mounted in a multiple press provided with automatic feed connections or the like to facilitate the manufacturing operation.

The metal for the balls is fed to the, dies in slugs of cylindrical contour, preferably cut from the end of a steel wire of a diameter depending upon the size of the bearing ball to be produced. In Fig. 1 a slug of the customary length and diameter for the size of balls to be produced in the dies illustrated is indicated in dotted lines at 4.

In Fig. 2 I have illustrated the approximate shape assumed by the metal of the slug in an intermediate position of the dies as they are brought together in the shaping operation. Generally speaking, the middle of the slug bulges outward under pressure of the dies to that the fibers of the metal which in the wire slugs are generally parallel with the length of the slug and consequently with the cylindrical surface of the slug, retain in general their parallelism with the surface of the slug except at the ends.

As the compression of the slugs in the dies is continued the diameter of the middle portion of the slug exceeds the diameter of the dies, as shown in Fig. 3, with the formation of a belt or ring of metal 5 around what maybe termed the equator of the ball. In this portion of the ball the metal of the slug is very much distorted, as indicated by dotted lines in Fig. 3, the degree of distortion depending largely upon the extent to which the diameter of the ring or belt exceeds the diameter of the semispherical die. In practice the mass of the slug is greater than the 3 capacity of the spherical dies so as to insure the metal filling the dies before they are closed.

In Fig. 3 I have illustrated approximately the relative size and shape of the dies and the slug of metal at a point in the manufacture ofthe balls when the dies are closed to the maximum extent that they are closed in the customary manufacturing operation. In Fig. 3 I have also illustrated the grain structure at this point in the manufacture of the ball and it will be noted that the fibers of the metal are turned outward at the middle point and are virtually radial throughout the ring or belt formed by the metal protruding from the die.

After the die-shaping operation above described the metal forming the belt orring around the middle of the ball is ground away to produce a spherical ball somewhat greater in size than the finally finished ball. This roughly dressed ball is then case-hardened in any desired manner and is then ground and polished to produce the finished ball of the desired size.

According to my preferred method of manufacture I employ in lieu of slugs of sufficient mass to fill the die cavity, slugs of slightly less mass and also slightly smaller diameter in proportion to the diameter of the ball.

In .Fig. 5 I have shown in dotted lines at 6 the dimensions of the cylindrical slug employed in my'new method for the production of balls of the same size-as made .by the old method from the slugs of the dimensions illustrated in Fig. 1. Fig. 6 shows a partial shaping of the ball at an intermediate stage in the closing of the dies. At this stage in the operation the re-shaping of the slug follows very much thesame pattern as in the old method except that as the ends of the slug are of smaller .area a greater portion of the exterior surface of the partially shaped ball is formed of the cylindrical surface of the original slug.

Fig. '7 shows the die-shaping operation completed. It will here be noted that the dies are completely closed and that the metal of the slug completely fills the spherical cavity formed by the closed dies except for small flat areas 1 at the bottom and top of the dies. These small flat areas are unavoidable in quantity production where tolerances in dimensions must be allowed in the interest 'of economical manufacture. However, the difference in the polar diameter of the shaped ball and the full diameter of the dies is so slight that no greater amount of metal :need be ground away in the finishing operation than necessary in the customary process of manufacture above described.

Fig. 8 shows the completed ball with the grain structure illustrated in dotted lines. As will be seen, the fibers of the steel extend insubstantial parallelism with the outer surface of the ball throughout the entire surface area except for very limited polar areas where the fibers are substantiallynonnalto the surface.

Balls made according to my new method have a much longer useful life than balls made according to the prevailing method above described. As will be seen from Fig. 4, wherein I have illustrated the grain structure of the finished ball made according to the usual procedure, the fibers of the steel through a comparatively large polar area and also throughout the equatorial band at the point where the extruded ring of metal is ground away in the first finishing operation, are substantially normal to the surface of the ball, leaving intermediate areas where the fibers follow the contour of thesurface. These intermediate areas are of such small dimensions that the metal under the impact of service is broken down and flakes away as indicated by the darkened portions marked 8 in Fig. 4. With the balls made according to my improved method this breakdown does not occur, and the useful life of the balls is prolonged until worn to such an extent that replacement is advisable.

My improved method of manufacture also has the advantage that one step in the process is avoided, namely, the grinding away of the ring of extruded metal before the hardening and flnishing operations, and also results in economy of metal, for, as stated above, the amount of metal which is removed in thefinishing operation is no greater in my new procedure than in the old method.

I claim:

1. The method of making metal balls which consists in placing between semispherical dies a mass of metal of slightly less volume than the volume of the cavity of the closed dies, closing the dies on the mass of metal to form .it into a generally spheroidal form having a mass slightly less than the volume of the cavity of the closed dies, and thereafter removing from the surface of the shaped mass sufficient metal for the .remaining mass to be truly spherical.

2. The method of making metal balls which consists in placing between semispherical dies a cylindrical mass of metal of slightly less volume than the volume of the cavity of the closed dies, closing the dies on the mass of metal to form a sphere having flattened areas lying within the general periphery of the sphere at diametrically opposite points, and thereafter removing from the surface of the shaped .mass suificient .metal for the remaining mass to .be truly spherical.

EMIL DEUSSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

